EP 0963105 A2 19991208 - Threshold matrix, and method and apparatus of reproducing gray level using threshold matrix
Title (en)
Threshold matrix, and method and apparatus of reproducing gray level using threshold matrix
Title (de)
Schwellenmatrix und Verfahren und Vorrichtung zur Wiedergabe von Grautönen unter Benutzung der Schellenmatrix
Title (fr)
Matrice de seuil, et procédé et appareil pour la reproduction de niveaux de gris utilisant la matrice de seuil
Publication
Application
Priority
JP 15445998 A 19980603
Abstract (en)
The present invention provides a threshold matrix that can obtain high-quality images with a uniform dot distribution using small masks and that can obviate the need to increase the mask size for a high-definition printer to reduce the memory capacity required to store the masks, as well as a gray-level reproduction method and apparatus using this threshold matrix. A threshold matrix is formed so that (1) a dot pattern generated by executing gray level processing using the threshold matrix has a set of element pixel blocks having in all gray levels the same dot distribution in each element pixel block corresponding to each element mask, so that (2) a low irregularity or pseudo periodicity is introduced into one of the low gray levels after the first gray level, so that (3) in all gray levels, the number of dots is equal for all element pixel blocks, and so that (4) every 4n ((n) is an integer) gray levels, the number of dots is equal for four partial element pixel blocks each obtained by dividing each element pixel block into four. <IMAGE>
IPC 1-7
IPC 8 full level
H04N 1/405 (2006.01)
CPC (source: EP)
H04N 1/4051 (2013.01)
Designated contracting state (EPC)
DE FR GB
DOCDB simple family (publication)
DOCDB simple family (application)
EP 99304306 A 19990602